Very unfavourable environmental conditions, which have resulted in a wide range of plant variability, have favoured types able to accommodate themselves to such conditions. Such reactions to stress gradually result in adaptation. The second article on this subject gives examples of adaptations of higher terrestrial plants to extreme temperatures (low or high), to scarcity or excess of water, to soil salinization or a high content of humus in soil, as well as biotic factors (browsing, trampling).
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